This invention claims the benefit of priority to Korean Patent Application No. 2001-13538 filed Mar. 16, 2001. The present invention relates to a touch panel with a polarizer integrally formed therein, a flat panel display with a touch panel integrally formed therein, and a laminating method thereof.
A touch screen has been known as an input device incorporated into or added to a computer, a portable transmitter, a spherical or aspherical displaying apparatus, a personal digital assistant (PDA), or the like. Although the touch screen (touch panel) is one of input devices, it has features that its input operation is simple, there is little possibility of wrong operation, and it is possible to input characters with hands, as compared with the other input devices such as a mouse or a keyboard.
As for the currently used touch panel, its concern or technical trend is being changed from a general function of an input device to high reliability, provision of a new function, durability, and a detailed technique such as fabricating technique related to a design and processing of material, substance or the like. Further, a detecting method, a structure and performance of the touch panel are well known in detail.
Considering briefly the detecting method, there is a resistive touch panel that is constructed by bonding together two sheets having different resistance components arranged such that the two sheets can be isolated by spacers and contacted with each other by a pressing action. Further, there are a capacitive touch panel, an ultrasonic wave touch panel, an optical (infrared) sensor touch panel, an electromagnetic induction touch panel, etc. Since they have properties different from each other according to their signal amplification problems or resolution differences and their degrees of difficulty of designs and fabricating techniques, the detecting methods should be determined in consideration of durability, economical efficiency and the like thereof in addition to optical property, electrical property, mechanical property, environmental resistance, input property and the like.
FIG. 1 is a sectional view showing the basic constitution of a resistive touch screen 10. An upper substrate 20 and a lower substrate 30 are structurally bonded by an adhesive 40 having thickness of approximately 75 to approximately 200 xcexcm with transparent conductive films 22 thereof faced to each other. The upper substrate 20 comes into contact with the lower substrate 30 by pressure applied upon depression for input. The upper substrate 20 is made of a PET film or a thin glass sheet, which is flexible. Since the thin glass sheet has an optical isotropy, it is used for reducing surface reflection of the substrate by attaching a polarizer onto the substrate. However, a plastic film having optical isotropy is recently available. Nevertheless, production costs, fabricating difficulty and physical property thereof is open to further improvement.
The detection of an input position is made by a structure configured such that the upper and lower substrates 20, 30 with electrodes put thereinto face each other with a gap of approximately 100 to approximately 300 xcexcm by means of dot spacers 50, and that input signals are extracted through a connector tail. As for its operation, when the upper substrate 20 comes into contact with the lower substrate 30 on an input point and a voltage is applied between the electrodes of the lower substrate 30, a potential gradient is produced on resistive surfaces between both electrodes. The resulting voltage is read through the electrodes of the upper substrate 20 and an X-axis input position is then calculated by a controller. Subsequently, a voltage is applied between the electrodes of the upper substrate 20 and the resulting voltage is read through the electrodes of the lower substrate 30 so as to calculate a Y-axis input position. Thus, the input point is shown on the display. By repeating the above procedures at a high rate, input positions are continuously shown on the display so that characters or lines are drawn.
Required characteristics of the touch panel are ones requested by a user in accordance with multiple purposes of the products for installing the touch panel therein. In order to meet these characteristics of the touch panel, the structure of the touch panel may be accepted to a certain extent through a partial structural modification of the touch panel. However, it is difficult to accept all the characteristics. In addition, there is a limit on acceptance of the required characteristics by means of the resistive touch panel only. Therefore, there is a need to select an optimal one of the structures or detecting methods of the touch panel suitable for the various required characteristics.
In view of the required characteristics, the resistive touch panel is suitable for daily life of the general public where the price, productivity, character writing and the like thereof have priority over all other things. An elastic wave touch panel is suitable for use in industrial equipments where the durability, optical property, insulating property, and the like thereof are of importance. Therefore, the characteristics of the touch panel depend entirely on selection of the touch panel by the user.
On the other hand, although there are many cases where an LCD is used for a display, the LCDs are classified according to usage of products because there are many types of LCDs. In order to classify the LCDs, various classifying manners are taken into consideration.
For example, it is possible to classify the LCDs into monochrome and color types, frontlight and backlight types, or STN and TFT types in view of their structures. In particular, due to the improvements of high resolution of the TFT and color yield of the frontlight LCD, there is a great demand for the touch panel to be mounted on the LCD.
In general, the length extending from an outermost periphery of a visual area of the touch panel to an outer periphery of the touch panel is called an inactive area. The miniaturization, thinness, and improvement in an effective area ratio of a screen of the products are needed. The inactive area of the LCD has been largely reduced, so that the inactive area of the touch panel should be necessarily reduced due to a limitation on an assembly structure of them, in which the dimension of the touch panel should be smaller than that of the LCD. However, the simple reduction of the inactive area of the touch screen produces problems that linearity and insulation shield of the electrodes are lowered, and it is likely that noise is produced due to easy intrusion of an electromagnetic wave and static electricity. Complementary technologies for the above problems have been continuously proposed.
The resistive touch panel is suitable for the daily life of the general public, as described above. However, the resistive touch panels still have a problem of whether it can exhibit an expected performance in combination with a display such as an LCD and meet various demands (required characteristics). This problem also applies to the other types of the touch panels.
FIG. 2 schematically shows a sectional structure manufactured by a technology of laminating the resistive touch panel onto the flat panel display according to the required characteristics thereof.
The structure of FIG. 2 is a flat panel display constructed in such a manner that a polarizer 60 is put on the bottom of a touch panel 10 comprised of an upper sheet 21 and a lower sheet 23, a liquid crystal display device 70 is put on the bottom of the polarizer 60, another polarizer 80 is then put on the bottom of the liquid crystal display device 70, and they are finally laminated together.
Here, the polarizers 60, 80 serve to convert visible rays into linearly polarized light on both sides of the liquid crystal display device 70 of the flat panel display. To this end, the polarizers 60, 80 are generally constructed by laminating together predetermined films such as transparent conductive films comprised of an upper base 61, an optical film base 62 and a lower base 63.
The technology of laminating the touch panel 10 onto the flat panel display by using the polarizers 60, 80 aims at enhancing light transmissivity as good as possible while maintaining all optical axes and simultaneously thinness and lightness thereof in view of its laminate structure. Various methods by which the maintenance of the optical axes can be achieved by measures such as use of optically isotropic materials and the light transmissivity can also be improved in view of the sectional structure by using optimal materials are advantageous to the thinness, miniaturization, and lightness thereof. The application of the laminate structure is taken into consideration at least within the range favorable to the thinness, miniaturization, and lightness thereof.
The concrete examples of the design of the touch panel are well known in Korean Patent Laid-Open Publication Nos. 1998-41100 and 1996-24536, etc. According to this technology, the polarizers have not been separately disposed, but integrally formed on the touch panel (the bottom thereof) while performing original functions of the polarizers. Although the technology has provided useful designs advantageous to the thinness, miniaturization, lightness, process improvements and low unit costs thereof, there has still been a problem of whether the light transmissivity, yield and reliability of the touch panel can be reliably maintained as the polarizers become integrally formed on the touch panel.
Cases where polarizers made of different bases are incorporated into or added to the touch panel, i.e., new polarizers themselves or a structure in which the new polarizers are used, have been well known. The above is schematically shown in FIGS. 3 and 4. The technology shown in these figures is used to more widely apply both the advantageous effects, which are obtained by incorporating the polarizer 60 into the touch panel 10, and the general results, which are produced in connection with selection of the bases of the polarizers 60, 80, to the laminate structures of the touch panel 10 and the flat panel display.
Examples of the laminate structure of the polarizers, the touch panel and the flat panel display, which are shown in the sectional structure of FIGS. 3 and 4, are as follows:
1. A structure of the polarizers 60, 80, including a laminate structure of the upper base 61, the optical film base 62 and the lower base 63.
2. A structure of the integrally formed polarizer 60, in which the transparent conductive film has been used on the polarizer 60 comprised of the lower base 63, the optical film base 62 and the upper base 61 from below, instead of the optically isotropic film.
3. A structure of the touch panel with the polarizer integrally formed therein, including the polarizer 60 with the transparent conductive film integrally formed therein, comprised of the lower base 63, the optical film base 62 and the conductive film from below; and the touch panel 10, comprised of the transparent conductive film and the upper sheet 21 which is constructed such that dot spacers 50 are applied to a bottom surface thereof and that electrodes 41 and a tail 42 are installed therein.
4. A structure of the touch panel with the polarizer integrally formed therein, including the polarizer 60 with the transparent conductive film integrally formed therein, comprised of the lower base 63, the optical film base 62, the upper base 61 and the conductive film from below; and the touch panel 10, comprised of the transparent conductive film and the upper sheet 21 which is constructed such that dot spacers 50 are applied to a bottom surface thereof and that the electrodes 41 and the tail 42 are installed therein.
5. A structure of the flat panel display with the touch panel integrally formed therein, including the polarizer 80 comprised of the lower base 63, the optical film base 62 and the upper base 61 from below; the liquid crystal display device 70 comprised of a lower glass sheet 72, a liquid crystal disposed between the lower glass sheet 72 and an upper glass sheet 71, and the upper glass sheet 71 from below, on the polarizer 80; the polarizer 60 with the transparent conductive film integrally formed therein, comprised of the lower base 63, the optical film base 62 and the transparent conductive film from below, on the liquid crystal display device 70; and the touch panel, comprised of the transparent conductive film and the upper sheet 21 which is constructed such that dot spacers 50 are applied to a bottom surface thereof and that the electrodes 41 and the tail 42 are installed therein.
6. A structure of the flat panel display with the touch panel integrally formed therein, including the polarizer 80 comprised of the lower base 63, the optical film base 62 and the upper base 61 from below; the liquid crystal display device 70 comprised of a lower glass sheet 72, a liquid crystal disposed between the lower glass sheet 72 and an upper glass sheet 71, and the upper glass sheet 71 from below, on the polarizer 80; the polarizer 60 with the transparent conductive film integrally formed therein, comprised of the lower base 63, the optical film base 62, the upper base 61 and the transparent conductive film from below, on the liquid crystal display device 70; and the touch panel, comprised of the transparent conductive film and the upper sheet 21 which is constructed such that dot spacers 50 are applied to the bottom surface thereof and that the electrodes 41 and the tail 42 are installed therein.
In the same as the conventionally designed structure, the structure of the polarizer with the transparent conductive film integrally formed therein, the touch panel with the polarizer integrally formed therein, the flat panel display with the touch panel integrally formed therein, or the like shown in the figures aims at diverse laminate structures of the transparent conductive film and further at thinness, miniaturization and lightness in view of the laminate structure thereof, in order to enhance the light transmissivity as good as possible while maintaining the optical axes.
However, in order to fabricate the laminate structure of the touch panel with the polarizer integrally formed therein, an issue as to how to apply or harmonize a process technology thereof to or with the laminate structure for accomplishing the touch panel with the polarizer integrally formed therein is more important than the modification of the bases of the polarizer and the laminate structure of the touch panel. Substantially, the process technology has caused these technical objectives to be limited.
In connection with the lamination process technology, the problems of the laminate structure of the conventional polarizer, the touch panel and the flat panel display, and the structural limitation thereof will be described below.
FIG. 5 shows schematically lamination processes in which the touch panel with the polarizer integrally formed therein is added to the flat panel display. First, a double-faced adhesive sheet 90 having an area similar to the sizes of the polarizer 60 and the touch panel 10 is beforehand prepared and one face of the double-faced adhesive sheet 90 is bonded to the lower sheet 23 of the touch panel 10 (step 1). After one face of the double-faced adhesive sheet 90 has been bonded to the lower sheet 23 of the touch panel 10, the other face of the double-faced adhesive sheet 90 is bonded to the upper base 61 of the polarizer 60 (step 2). After the above step has been completed, the lower sheet 23 of the touch panel 10 and the lower base 61 of the polarizer 60 are combined together with each other by the double-faced adhesive sheet 90. Then, by bonding the upper sheet 21 and the lower sheet 23 of the touch panel 10 together, the upper substrate 20 and the lower substrate 30 are combined together, and thus, the integrated touch panel 10 is accomplished (step 3). In a case where the touch panel 10 with the polarizer integrally formed therein is laminated (bonded together) onto the flat panel display, the touch panel is laminated onto the top of the flat panel display in such a state where the same double-faced adhesive sheet 90 that has used in the above steps is interposed between the polarizer 60 and the upper glass sheet 71 of the liquid crystal display device 70. In the same way, the polarizer 80 is bonded together to the lower glass sheet 72 with the double-faced adhesive sheet 90 interposed therebetween, and the touch panel 10 is then laminated onto the flat panel display (step 4). Most of the above lamination processes (steps) have an atmosphere in which appropriate heat and laminating pressure can be transferred. Although a part of the lamination processes may be changed, the process for bonding together the polarizer 60 and the lower sheet 23 of the touch panel is performed before the process for bonding the upper and lower sheet 21, 23 of the touch panel 10 in a case where the double-faced adhesive sheet 90 is used. The reason is that distortion of the touch panel, dislocation of the upper and lower substrates, and heat deformation cannot be avoided due to the pressure applied thereto if the touch panel 10 is bonded to the polarizer 60 in a state where the upper and lower sheets 21, 23 have been bonded together into the touch panel.
FIG. 6 shows schematically lamination processes in which the other touch panel with the polarizer integrally formed therein is added to the flat panel display. Here, the dot spacers 50 for insulating the upper and lower substrates 20, 30 from each other are formed on the upper sheet 21 of the upper substrate 20 rather than on the lower substrate 30.
Such a structure is considered as the structure for making a preparation against a problem that may be produced during the lamination processes because the dot spacers 50 are placed on the lower substrate 30 of the touch panel 10, that is, a likelihood that a desired insulation within the active area cannot be obtained since the dot spacers 50 is pressed down (collapsed) by the pressure for pressing down the dot spacers 50 during the above steps 1 and 2 in which the polarizer 60 is pressed from the top of the lower substrate 30. In case of this structure, however, the shock applied upon contact with the upper substrate 20 is greater than that in the lower substrate 30. Thus, it is more likely that the dot spacers 50 will be removed from the transparent conductive film 22.
Further, there are other problems in that planar bonding uniformity cannot be ensured because the processes should be performed twice if the double-faced adhesive sheet 90 is used upon bonding of the touch panel 10 and the polarizer 60, and in that deterioration of the transmissivity and the yield can be produced due to formation of minute air gaps between the contact surfaces during the lamination processes.
When the touch panel with the polarizer integrally formed therein constructed as such in the form of a laminate structure is incorporated into the flat panel display, the laminate structure of the touch panel with the polarizer integrally formed therein and the flat panel display, wherein the light transmissivity should be enhanced as good as possible while maintaining optical axes and the laminate structure is advantageous in view of thinness and lightness thereof, has a strong likelihood that fatal defects such as loss of the light transmissivity and deformation of the active area of the touch panel resulting from the air gaps will be produced during the lamination process. Further, since the laminating method thereof should be prepared against the above likelihood, the yield and reliability of the products are very dependent on the lamination processes. Thus, the conventional structure or method has remained at a lower state of the art.
An object of the present invention is to provide a laminate structure of a touch panel with a polarizer integrally formed therein or a flat panel display with the touch panel incorporated thereinto that is advantageous in view of thinness and lightness thereof.
Another object of the present invention is to provide a polarizer suitable for the touch panel with the polarizer integrally formed therein.
A further object of the present invention is to improve light transmissivity by reducing air gaps produced in the laminate structure of the touch panel with the polarizer integrally formed therein.
A still further object of the present invention is to provide a method wherein defects in an active area of the touch panel can be reduced when fabricating the touch panel with the polarizer integrally formed therein and laminating the touch panel into the flat panel display.
According to an aspect of the present invention for achieving the above objects, there is provided a touch panel with a polarizer integrally formed therein, which comprises a touch panel including an upper substrate having an upper sheet and a transparent conductive film formed below the upper sheet, a lower substrate having a transparent conductive film like the transparent conductive film of the upper substrate and a lower sheet formed below the transparent conductive film, dot spacers for insulating the upper and lower substrates from each other, and electrodes for applying voltage to a resistive film disposed between the upper and lower sheets; and a polarizer bonded to the lower sheet of the touch panel for converting visual light to linearly polarized light, characterized in that: the polarizer is sequentially comprised of an upper base, an optical film base and a lower base; and an adhesive layer, which is bonded together to the lower sheet of the touch panel and causes the polarizer to be integrated with the touch panel in order to manufacture a laminate structure thereof, is further provided on an upper face of the upper base of the polarizer.
According to another aspect of the present invention, there is also provided a touch panel with a polarizer integrally formed therein, which comprises a touch panel including an upper substrate having an upper sheet and a transparent conductive film formed below the upper sheet, a lower substrate having a transparent conductive film like the transparent conductive film of the upper substrate and a lower sheet formed below the transparent conductive film, dot spacers for insulating the upper and lower substrates from each other, and electrodes for applying voltage to a resistive film disposed between the upper and lower sheets; and a polarizer bonded to the lower sheet of the touch panel for converting visual light to linearly polarized light, characterized in that: the dot spacers formed between the respective transparent conductive films of the upper and lower sheets are formed on the lower sheet so that the upper and lower substrates can be laminated to each other; the polarizer is sequentially comprised of an upper base, an optical film base and a lower base; an adhesive layer, which is bonded together to the lower sheet of the touch panel and causes the polarizer to be integrated with the touch panel in order to manufacture a laminate structure of the touch panel, is provided on an upper face of the upper base of the polarizer; and another adhesive layer for causing the polarizer incorporated into the touch panel to be bonded to an upper glass sheet of a liquid crystal display device is provided on a lower face of the lower base of the polarizer.
According to a further aspect of the present invention, there is also provided a flat panel display with a touch panel integrally formed therein, which comprises a touch panel including an upper substrate having an upper sheet and a transparent conductive film formed below the upper sheet, a lower substrate having a transparent conductive film like the transparent conductive film of the upper substrate and a lower sheet formed below the transparent conductive film, dot spacers for insulating the upper and lower substrates from each other, and electrodes for applying voltage to a resistive film disposed between the upper and lower sheets; a polarizer bonded to the lower sheet of the touch panel for converting visual light to linearly polarized light; a liquid crystal display device bonded to the polarizer and including an upper glass sheet, liquid crystals and a lower glass sheet; and another polarizer bonded to the lower glass sheet of the liquid crystal display device, characterized in that: the dot spacers formed between the respective transparent conductive films of the upper and lower sheets are formed on the lower sheet so that the upper and lower substrates can be laminated to each other; the polarizer bonded to the lower sheet is sequentially comprised of an upper base, an optical film base and a lower base, and further comprises an adhesive layer, on an upper face of the upper base thereof, which is bonded together to the lower sheet of the touch panel and causes the polarizer to be integrated with the touch panel, and another adhesive layer for causing the polarizer incorporated into the touch panel to be bonded to an upper glass sheet of the liquid crystal display device, on a lower face of the lower base thereof, and the polarizer bonded to the lower glass sheet of the liquid crystal display device is sequentially comprised of an adhesive layer, an upper base, an optical film base and a lower base, is then bonded to the lower glass sheet of the liquid crystal display device.
According to a still further aspect of the present invention, there is provided a method for manufacturing a flat panel display with a touch panel integrally formed therein by bonding one face of a polarizer to a lower sheet of the touch panel, forming a laminate structure of the touch panel with the polarizer integrally formed therein, and bonding the opposite face of the polarizer of the touch panel with the polarizer integrally formed therein to an upper glass sheet of a liquid crystal display device, comprising the steps of: forming dot spacers on a transparent conductive film of the lower sheet and bonding upper and lower substrates of the touch panel with transparent conductive films of upper and lower sheets facing each other; bonding the lower sheet of the touch panel to an adhesive layer formed on one face of the polarizer; and bonding the upper glass sheet of the liquid crystal display device to an adhesive layer formed on the opposite face of the polarizer bonded with the lower sheet.
According to the touch panel with the polarizer integrally formed therein of the present invention, the constitution thereof is advantageous in view of lightness, miniaturization and thinness thereof. Further, according to the process of laminating the touch panel with the polarizer integrally formed therein and the flat panel display with the touch panel integrally formed therein, loss of the light transmissivity can be reduced and defects resulting from deformation of the active area of the touch panel can be simultaneously removed by preventing formation of minute air gaps beforehand. Furthermore, yield and reliability of the laminating process can be highly maintained.
Further objects and advantages of this invention will be apparent from the following detailed description of the presently preferred embodiments which are illustrated schematically in the accompanying drawings.